“In your opinion, did the officer have only two reasonable options - tasing or a struggle - when the driver walked away?”
Yes.
“Does tasing someone along a busy highway put his life at increased risk beyond walking along the highway in full control of his faculties?”
Yes.
(Just to minimize branching off, I’ll give you this.)
There is no evidence the officer stated “you are under arrest”.
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Did the officer have reason to believe that the driver was being uncooperative, and resisting arrest?
Is a law enforcement officer required by law to put the life and safety of someone resisting arrest above his own?
Uncooperative: The officer might have a case, but Massey did follow instructions between being ordered out of the vehicle and when the taser was pulled.
Resisting arrest: No.
Is a law enforcement officer required by law to put the life and safety of someone resisting arrest above his own?
No.
There is no evidence the officer stated "you are under arrest".
What about your claim that the driver said, "No, you're not", when other posters have very clearly stated that they heard "No, I'm not".
It's relevant to your question of Massey's cooperation.